Light Pollution Suppression (LPS) Filters

Light pollution suppression (LPS) filters are designed
to suppress the common emission lines generated by
artificial lighting, yet allow the important nebula
emission lines to pass, thus enhancing the contrast of
astronomical objects, particularly emission nebulae
(see filter plots).
The most recently introduced version (D2) has a bandpass designed
to cope with the increasing trend of society's switch to LED lighting.

Unlike other light pollution suppression filters,
IDAS filters are specifically designed
for balanced color transmission using the IDAS unique
Multi-Bandpass Technology (MBT) process. The balanced
transmission allows color photographs to be taken with
minimal color cast to broadband emission objects such as
stars, galaxies and globular clusters.

CCD imaging can also benefit, because although CCD
imagers can already shoot through light
pollution to some extent, including an LPS filter
to the setup gives an added (signal-to-noise) edge as shown in
these CCD examples (comparison
testing by G. Tomita in Tokyo).

Note, however, that light pollution suppression filters
are not a perfect substitute for dark skies.
Refer to our discussion of the limitations and common misconceptions
about light pollution suppression filters.

LPS filters are available for 1-1/4" and 2" (48mm)
eyepieces, as well as in numerous sizes to
accomodate most popular camera lenses.
Each filter lot is tested and a plot of the
spectral response of the lot is provided with each
filter (see filter
plot sample).